1. Field of the Invention
The present invention relates generally to a method and apparatus of detecting and locating leaks in a pipe system, and in particular, to a method of determining and locating leaks in conduits having an inner pipe carrying a liquid, an outer pipe surrounding the inner pipe and a filler material in an annular space between the inner and outer pipes.
2. Description of the Related Art
Conduits are, for safety reasons, composed of an inner pipe carrying a liquid medium and an outer pipe enclosing the inner pipe. In practice, it is necessary to detect a leak in one of the walls as quickly and easily as possible and to determine the location of that leak. When a leak occurs, either the liquid medium inside the inner pipe or water present on the outside of the outer pipe enters into the space between the inner and outer pipes.
In older pipe systems, it has been difficult to detect and locate defects resulting in leaks, because perspiration tended to form in air spaces between the pipes due to changes in temperature (breathing). Hence, when conventional type sensor cables were introduced, they often reported defects, whether or not a leak was actually present. For example, in sewer systems, the space between sewer pipes is often filled with foamed concrete for reasons of stability. This concrete is wet by nature and consequently unsuitable for leak monitoring. If a leak occurs within such a conduit, the filler material becomes wetter at the location of the leak in the space between the pipes. However, this increased wetness cannot be detected quickly at the accessible ends of the pipes either optically or by measuring technology methods.
In newer installations, the pipes are stabilized relative to one another, that is, the space between the pipes is filled with foam which keeps that space dry. However, if the foam has closed pores this can greatly delay detection of a leak. Also, if the foam has open pores, the damage spreads, making it harder to locate the leak.